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sata_nv: delay on switching between NCQ and non-NCQ commands 

This patch appears to solve some problems with commands timing out in
cases where an NCQ command is immediately followed by a non-NCQ command
(or possibly vice versa). This is a rather ugly solution, but until we
know more about why this is needed, this is about all we can do.

Signed-off-by: Robert Hancock <hancockr@shaw.ca>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This commit is contained in:
Robert Hancock 2007-02-19 18:42:30 -06:00 committed by Jeff Garzik
parent cc0759103f
commit 5e5c74a5e1
1 changed files with 10 additions and 0 deletions
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10
drivers/ata/sata_nv.c
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@ -219,6 +219,7 @@ struct nv_adma_port_priv {
void __iomem * gen_block;
void __iomem * notifier_clear_block;
u8 flags;
int last_issue_ncq;
};
struct nv_host_priv {
@ -1260,6 +1261,7 @@ static unsigned int nv_adma_qc_issue(struct ata_queued_cmd *qc)
{
struct nv_adma_port_priv *pp = qc->ap->private_data;
void __iomem *mmio = pp->ctl_block;
int curr_ncq = (qc->tf.protocol == ATA_PROT_NCQ);
VPRINTK("ENTER\n");
@ -1274,6 +1276,14 @@ static unsigned int nv_adma_qc_issue(struct ata_queued_cmd *qc)
/* write append register, command tag in lower 8 bits
and (number of cpbs to append -1) in top 8 bits */
wmb();
if(curr_ncq != pp->last_issue_ncq) {
/* Seems to need some delay before switching between NCQ and non-NCQ
commands, else we get command timeouts and such. */
udelay(20);
pp->last_issue_ncq = curr_ncq;
}
writew(qc->tag, mmio + NV_ADMA_APPEND);
DPRINTK("Issued tag %u\n",qc->tag);